The injectable drug is given once every six months to increase bone mass and strength.

Analysts think Prolia should bring Amgen billions in revenue after it is approved. Sales of the company's former top sellers, the anemia drugs, Aranesp and Epogen, have dropped in recent years due to safety concerns and label restrictions.

Pill-based osteoporosis drugs, such as Fosamax and Zometa, have been available for more than a decade. But Amgen Executive Vice President Dr. Roger Perlmutter said many women can't tolerate those drugs or have trouble remembering to take a daily medication.

One out of every two women over age 50 will break a bone in their lifetime due to osteoporosis, which causes bones to become brittle, according to an FDA statement.

FDA approved the drug based on a 7,000 patient study conducted by Amgen that showed reduced vertebrae and hip fractures in postmenopausal women.

Common side effects with the drug included back pain, high cholesterol and urinary bladder infections.

The Food and Drug Administration on Tuesday approved Amgen's bone strengthening drug, Prolia, for postmenopausal women at risk for fractures, a potential blockbuster market.The injectable drug is given once every six months to increase bone mass and strength.Analysts think...